题干
In spite of the great difficulties, Helen Keller ______ studying and finally succeeded.
A：stuck to
B：kept up with
C：kept o
D：insisted o
答案(点此获取答案解析）
C
数
满足
，且在－3，－2上是减函数，
是钝角三角形的两个锐角，则下列不等式关系中正确的是